The invention relates to the technical field of floor coverings comprising a double stiffening and rollable reinforcement. These reinforcements are of the type made from a layer of non-woven polyester material.
Initially, with reference to FIG. 1, the covering (R1) is of the type comprising a sheet of controlled thickness—typically 0.5 to 3 mm—having a shore A hardness of between 60 and 90 prepared by known techniques of processing thermoplastic polymers: coating; calendering; extrusion. Preferably, the polymer used is plasticized PVC, but any other thermoplastic polymer can be used. On the back, the covering includes a reinforcement (2) consisting of a non-woven polyester bonded to a glass grid. Specifically, the non-woven material has a weight of 15 to 40 g/m2 preferably 25 g/m2 and the glass grid consists of glass yarns. These have a denier of 34 or 68 Tex distributed in a density varying between 1*1 and 5*5 yarns/cm in warp and weft with all possible asymmetric intermediate combinations. The covering includes a foam (3) for bonding to the floor. This foam is made from PVC, but any other thermoplastic polymer can be used. The foam thickness ranges from 1 to 10 mm and preferably from 3 to 8 mm.
The new regulation DTU 13.3 requires the elimination of any possibility of having, on the back of the material and joined to the foam, a non-woven back allowing the use of moisture resistant adhesives that are impossible to use with a back not lined with a non-woven material. This is explained by the fact that moisture resistant adhesives (PU 2 components or PU/Epoxy 2 components for example) have a very low adhesion to plasticized PVC. Furthermore, they have no “tack”, making it impossible to lay the covering.
To meet this regulatory requirement, the solution was therefore to have on the back of the covering material a non-woven back capable of constituting a screen with the front part of the covering and of absorbing the entry of adhesive.
In the case of thin materials without a foam sub-layer, the problem is easily solved by the lamination of a non-woven structure on the back of the surface material.
On the contrary, for materials with a foam sub-layer, a first difficulty stems from the fact that the foam thickness prevents or hinders the bending of the material by the twin layer effect of the two reinforcements. With reference to FIG. 2 of the drawings, the covering (R2) answering to this definition comprises a calendered sheet (1) in one or more thicknesses, a structure of the type described for the covering (1), adding thereto a second reinforcement (4) of non-woven polyester material of the same type, with a grid and a polyester non-woven layer.
One problem raised by this type of covering resides in the fact that the double reinforcement forming a twin layer prevents the uniform rolling of the covering. FIG. 2A shows the covering (R2) of FIG. 2 in the rolling phase, that is with a curved shape, and, a situation of splitting and/or fracture of the non-woven material (2b) from these fibers with regard to the grid (2a) can be observed on the first reinforcement (2). FIG. 2B shows the final appearance of the unwound covering with the appearance of defects (2c) on the visible front side due to the torn non-woven material. This unattractive appearance is unacceptable to the customer. The pull exerted on the non-woven part of the first reinforcement during the rolling causes the fibers to tear.
This indicates a double drawback of difficulties in rolling the covering on itself, which inherently causes the fracture of one of the reinforcements and the loss of attractiveness of the product.
The Applicant's approach was therefore to seek to remedy these drawbacks.
In practice, and initially, tests were performed taking account of the variation in thickness of the various components of the covering, thereby trying to improve the constitution of the first reinforcement. The results did not prove satisfactory, and drawbacks subsisted to various degrees. The difficulty to be solved was to design a covering appropriate to the problems raised, but which is designed with a double reinforcement to meet the standard DTU 13.3.
The Applicant's approach was accordingly to examine the rolling conditions and the resulting physical effects.
It is therefore based on this problem and on this aforementioned approach that the Applicant considered modifying the structure of the first reinforcement of the covering, while preserving its principle in combination with the second reinforcement to put the solution of the invention into practice.